LUTHERIE

Step 14: Applying the Finish

Perhaps no other aspect of lutherie is quite as controversial as the subject of finishing. Ask any luthier about his thoughts on the matter and he will no doubt bend your ear on what constitutes a "proper finish."

There are really four basic types of finishes for stringed instruments: Nitrocellulose lacquer - brushed or sprayed; water-based lacquer - brushed or sprayed; spirit varnish - usually shellac flakes dissolved in alcohol and applied with a pad (french polishing); and oil varnish. As far as I can tell through reading and experimentation, what kind of finish you use should be determined by your needs, your abilities and your equipment. There are plenty of scources for research on each, and I'll leave the merits and faults to the experts.

After weighing my options, I decided to try water-based brushing lacquer. Those of you who have been following this tale from the beginning will recall that I intended to french polish the body and apply an oil finish to the neck. Well, after further investigation, I realized that french polishing required much more finesse and time than I had. Further, it is such a thin coating that any flaws in my woodwork would stand out. I bought a pint of clear gloss sealer and one of brushing lacquer from Stew-Mac. The brushing lacquer contains a retarder that slows the drying time a little and helps the finish flow out more evenly after application. At this time, I don't want to invest in a spray rig or in building a suitable booth, so brushing is the only practical solution for me.

There is no way around prepping the wood before finishing. Take your time and get every inch of your instrument as smooth and even as you possibly can. If you don't, you'll see the flaws through the finish and it will eat at you every time you pick it up. After applying and sanding back the grain filler, sand with a small rubber or cork block whenever possible and sand only with the grain, starting with 220-grit and proceeding through 320, 400, and 600. At this point you may decide, as I did, to go on through the Micro-Mesh grades, beginning with 1500. I see no reason to go beyond 3600 at this stage. wet the wood down lightly after 320-grit and allow it to air dry. This will raise the grain and then you can sand with the same grit to remove the resulting fibers that stick up.

On mahogany, rosewood, walnut or other "open pored" woods, you must fill the pores in order to achieve a smooth surface for your finish. I needed a water-based filler to be compatible with my laquer and I experimented with several types - all unsatisfactorily. Just because it says that it's mahogany colored doesn't mean it is! I tried adding acrylic paint to it as recommended to bring the color up to my desired shade, but no dice. I finally settled on two shades of Elmers wood filler that, when combined, made a pretty good match with my wood. This stuff can be found at Home Depot and is very cheap. It's water-based and is easy to apply. Just thin it down with water, spead it on your wood and work it into the pores - across the grain - with a plastic spatula or an old credit card (I used and expired driver's license). Wait until it dulls all over and wipe off the excess. Let it dry overnight and sand it back down to wood - with the grain - using 220-grit, no-fill paper. I did the whole uke twice and got a nice smooth surface. If you have wood inlay such as my herringbone purfling and backstrip, you'll want to mask it before filling so as not to darken it.

When the filling is complete, perform your sanding regimine as described above. When you are satisfied that you've done your very best, you are ready to stain the wood if you choose - water based stain - or you can move on to the sealer coats. After experimenting on scrap mahogany, I decided that instead of staining the wood to darken it, I would apply color coats after sealing and before the clearcoats of laquer. More on that in a minute.

Before proceding further, I decided that it was time to attach the neck for the final time. It is certainly possible to wait until the finishing is complete to do this, but I thought that it would make the uke easier to handle. In retrospect, I believe that it was a good decision. Be sure to mask your fingerboard at this time to prevent any of the various finishes from getting on it.

I fretted about whether or not to use glue as well as the bolts to secure the neck heal to the body and finally decided on a compromise of sorts; I used liquid hide glue on the heel joint as well as the fingerboard-to-body joint. This glue allows disassembly with heat and moisture if it becomes necessary to remove the neck for reset or repair. I spread glue on all mating surfaces and bolted the neck to the body. I then clamped the fingerboard extension to the body and let all dry for several hours.

Using a foam brush, I began applying the sealer. This basically a high-solids version of the brushing laquer that...well...seals the wood and prevents your topcoats from being soaked up by the bare wood. It also aids with pore filling and fills the little gaps in your binding, purfling, etc. I used two coats on the top and three everywhere else, sanding lightly with 320-grit in between. Wait two hours between coats and overnight before starting the color or top coats.

Any further photos of me brushing various substances onto the uke would be redundant, so from here I'll just desribe what I did.

As I mentioned earlier, I decided that I liked the look of color coats rather than stain for darkening the mahogany. Experiments on scrap showed that the stain masked the natural luminescence of the wood while a couple of coats of the clear laquer containing several drops of concentrated stain darkend the wood while letting its character show through. Now please note that I was using a water-based stain in my experiments. I feel sure that an oil-based stain would have given better results. If you're using nitrocellulose laquer or oil for your topcoats, then an oil stain might be the way to go.

You must use caution when sanding between color coats. You do not want to sand through these coats or your color will be uneven. As with the filler, mask your wood inlays so as not to darken them with the color coats. Wait overnight before proceeding to the topcoats.

Now you can begin your final coats. dip your foam brush in the laquer and allow the excess to drip off, turning the brush over a couple of times. Brush a piece of scrap a time or two to gage that the laquer is free of bubbles and not too thick on the brush. Now drag the brush across the surface of the instrument (with the grain) at a slow but steady pace, feathering it off of the edges to avoid "pooling" as you lift off. Overlap the next stroke only by 1/8" or so to avoid ridges in the finish. Keep the uke level when you complete each surface and allow 15-30 minutes for the laquer to flow out and set up. If you're in a big hurry, you can expose your fresh finish to infrared light and it will set up in couple of minutes. Cover the top, sides, back neck and peghead in this manner and let it rest overnight

Sand this first coat lightly with very fine paper - I used 1800-grit Micro-Mesh wrapped around an art gum eraser. Pay particular attention to flattening any ridges created by the brush. this is not a major sanding, but a "smoothing" to provide the next coat with a relatively flat surface. As you procede, your technique will improve and there will be less need to sand back between coats. If you wait overnight, however, sand lightly to scuff the finish so that the next coat will have something to grip. I applied 4 coats to the top and 5 everywhere else. I wanted the top to have as few as possible so that it would be as "live" as I could make it. You'll know when you've applied enough finish: the surface will be completely filled and smooth, with no pores or grain showing.

You will need to wait at least a week for the finish to cure before final sanding and polishing. I used that time to finish my bridge and to acquire and install my name in gold lettering to the peghead. I did not apply the topcoats to this area because I needed to place this lettering under the finish. I agonized over the various ways to do the lettering and finally settled on some very high quality,metallic gold, stick-on letters created for me by FastSigns. We went over the various fonts available and selected a semi script about 3/8" tall and 2" wide with a 5 degree radiused arc to match the top of the peghead. It took six coats of clear lacquer to cover.

When the week was up, I began final sanding. The object here is to "flatten" the finish, removing high spots. I wet-sanded this time using water with a drop or two of dish soap, starting with 1800 Micro-Mesh and going all the way to 12000 on the body. Because I intended to leave a satin finish on the neck, I stopped with 3600 there. Sand with the grain and do so lightly, wiping the sludge off and checking your progress in a good light. This is tedious, but satisfying work. There may be a few "squiggles" in your finish that refuse to come out and there may also be a hazy quality to the finish, even after the 12000-grit, but these will come out when you do the final buffing.

Using an old drill, a vise, and a flannel buffing wheel that I found at Harbor Freight Tool Co., I made a very adequate buffer for $10. I used a plug-in lamp dimmer as a speed control and practiced on scrap until I found a good speed that buffed but did not melt the finish. I bought some really good Menzerna "Fine" grade buffing compound from Stew-Mac and held it against the wheel for a few seconds before proceeding. Mask off the fingerboard and the neck unless you want the neck to be a high gloss. Make sure that you keep a good grip on your instrument at all times! The buffer will snatch it out of your hands and send it flying before you know what happened! Buff across the grain, keeping the uke moving all the time to avoid burning the finish. Then buff with the grain with less pressure. Be extra careful with the edges; you can go through the finish there very quickly. Recharge the wheel with compound as needed. This all goes very quickly, and you won't believe how incredible it looks with very little effort.

I then masked off the neck and body surrounding the fingerboiard and applied an oil finish. I used Tru Oil, which was originally made for finishing gunstocks. It has been found to be the best commercial oil finish for instruments and is recommended by many luthiers. It is so easy to use that it should be against the law. Wipe it on with a rag and wipe it off immediately. It will dry nicely overnight and not be sticky or greasy at all. Do this a couple or three times and wait a week. Polish it with 0000 steel wool or Micro-Mesh and you will have a rich "open pore" finish with a good sheen. It darkens like a stain, so practice on scrap to be sure what you're getting. I have already decided to finish an entire instrument this way in the future. It won't hide your mistakes, however, so good prep is an absolute requirement.

Now is a good time to attach the bridge. I finished shaping it and applied the same oil finish that I used on the fingerboard. Measure your scale length from the nut to the middle of your saddle slot and stick the bridge to the top with double sided tape. Measure from the body/neck joint at the twelth fret to the corners of the bridge to assure that the bridge is perfectly aligned. Place tape several layers thick around the bridge to mark off its boundries and measure again to make sure it hasn't moved. Remove the bridge and scrape away the finish down to the bare wood. I used a single edge razor blade broken it half. I "turned a hook" in the edge like a scraper blade and carefully removed the 4 layers of topcoat, two layers of color coat and two of sealer. Don't scrape right to your taped line, but rather leave a 16th of finish so that the bare wood doesn't show under the bridge.

Spread a thin layer of TiteBond on both surfaces and clamp the bridge down as shown, using wood scraps or cork, etc. to pad and protect the wood inside and out. Let set and hour and don't put stress on the joint for at least 24 hours. Be sure to measure again before the glue dries to insure correct alignment. Clean up any squeeze-out with a damp cloth. Notice the gloss on the top after buffing!

Though it's really hard to convey a sense of the quality of the finish with a cheap digital camera on the web, here are some shots of the concert uke with the finishing completed. I must say that I'm extremely pleased with the results - especially given that it was my first attempt at a really fine glossy laquer treatment. I managed to get a good smooth gloss finish without that "dipped in plastic" look that some of the less expensive production guitars have. All I can say is "don't be afraid!" If I can do it, so can you.

All that's left at this point is to fit the nut and saddle, install the tuning pegs, and string it up. I guess that I don't have to tell you that the word "excited" doesn't quite measure up to my true feelings about completing this project - my first instrument. stay tuned!